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"July 2002" / Bibliography: leaves 185-247. / xvi, 247 leaves : ill., plates (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / "Paternal heat stress has been reported not only to damage spermatogenesis, endocrine and biochemical functions of testicular tissues, but also to affect the development of preimplantation, implanting and post-implantation embryos in both animals and humans. However, the relationship between the development of preimplantation embryos and the extent of damage of germ cells during heating has not been considered in detail and the molecular mechanisms underlying the effect of paternal heat stress on the development of embryos have not been investigated. These issues form the focus for the studies presented in this thesis. All work was undertaken in mice, using F1 C57/CBA progeny." -- Abstract / Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 2002

Mammalian preimplantation embryo development is prone to high rates of early embryo demise. Two underlying causes for failed development include the effect of sub-optimal culture media and maternal lethal effect (MLE) genes. In line with the growing evidence, we hypothesize that embryo fate is determined by the outcome of specific intracellular interactions between pro- and anti-apoptotic proteins under suboptimal culture conditions such as HTF medium and oxidative stress. Characterization of Nalp5, a MLE gene resulting in 2-cell embryo arrest, also found a significantly higher expression of pro-apoptotic proteins in knockout oocytes and embryos. With the use of two anti-apoptotic peptides, TAT-BH4 and Bax-inhibiting peptide (BIP), we attempted to improve embryo development. Our results found that neither peptide was able to improve embryo development in the Nalp5 model, or the HTF model. However, TAT-BH4 is capable of significantly improving developmental competence in embryos cultured under oxidative stress. Our findings suggest that supplementation of TAT-BH4 in embryo culture medium may offer a novel and cost-effective technique to improve embryogenesis of cultured embryos. However, further studies are still required.

Mammalian preimplantation embryo development is prone to high rates of early embryo demise. Two underlying causes for failed development include the effect of sub-optimal culture media and maternal lethal effect (MLE) genes. In line with the growing evidence, we hypothesize that embryo fate is determined by the outcome of specific intracellular interactions between pro- and anti-apoptotic proteins under suboptimal culture conditions such as HTF medium and oxidative stress. Characterization of Nalp5, a MLE gene resulting in 2-cell embryo arrest, also found a significantly higher expression of pro-apoptotic proteins in knockout oocytes and embryos. With the use of two anti-apoptotic peptides, TAT-BH4 and Bax-inhibiting peptide (BIP), we attempted to improve embryo development. Our results found that neither peptide was able to improve embryo development in the Nalp5 model, or the HTF model. However, TAT-BH4 is capable of significantly improving developmental competence in embryos cultured under oxidative stress. Our findings suggest that supplementation of TAT-BH4 in embryo culture medium may offer a novel and cost-effective technique to improve embryogenesis of cultured embryos. However, further studies are still required.

Background and Objectives: Pre-implantation Genetic Diagnosis (PGD) is an established alternative to prenatal diagnosis to select genetically disease-free embryos in vitro before they are transferred back to the mother, and it has gained acceptance for couples at risk of passing on monogenic diseases and chromosomal abnormalities around the world. More PGD cycles in conjunction with in vitro fertilization (IVF) have been offered to the Asian couples in Hong Kong who are carriers of genetic diseases or chromosomal abnormalities. This study evaluates the attitude and moral concerns towards PGD of the enrolled couples, and their knowledge of their underlying genetic conditions. Methods: This cross-sectional survey was carried out between June2013 and March 2014. All the couples enrolled in the PGD program at the Queen Mary Hospital were invited to join the study. Total 47 couples and 2 women, whose male partners declined to respond, were recruited. Self-reported structured questionnaires were completed by participating subjects. Statistical analysis was performed to study the attitude and concerns related to different PGD stages, genetic conditions, experience of past pregnancies and sex of the surveyed participants. Results and discussion: Ninety-six completed questionnaires were analysed with 36.5%from the Pre-PGD group, 31.2%from the PGD Treatment group and 32.5% from the Post-PGD group. There was a trend of increase in psychological stress and concerns related to the IVF/PGD related procedures when couples proceeded from the pre-PGD to the post-PGD stage. A good acceptability of PGD related procedures and similar moral value about the embryo fate, comparable to overseas studies, were observed, except we had a lower percentage of subjects (25%) who expressed no concern about repeated IVF cycles. The worries about the transfer of carrier embryos were high (33%)among couples who are thalassemia carriers. While 15% of the subjects disagreed with termination of pregnancy for a genetically confirmed abnormal IVF/PGD fetus,18% of the subjects could not decide at the time of the study. So counselling support to the couples when they face the above two difficult situations is important. We also found majority of the subjects (76%) optedto tell their children later about their conception. Support for parents to access counseling advice at their preferred time of disclosure is therefore worth considering. Regarding the knowledge of the couples on their underlying genetic conditions, most subjects (95%)knew their carrier status well. Most subjects (89%) with single gene disorder knew their recurrent risk of having an affected baby but only 32% could tell the inheritance pattern. Estimation of recurrent risk is more difficult for the group with balanced chromosomal translocation. Significance: This first study in Hong Kong on the Chinese couples enrolled in the PGD program highlights the specific concerns of the couples with different underlying genetic conditions at the different stages of PGD. The findings could serve as local reference to guide future studies and the development of PGD counseling services and follow-up for the couples seeking such intervention in the future. / published_or_final_version / Paediatrics and Adolescent Medicine / Master / Master of Medical Sciences

Thesis (doctoral)--Technische Universität, Dresden, 2006. / Includes bibliographical references and sources (p. [247]-274) and glossary.

Thesis (Ph. D. in Religion)--Vanderbilt University, May 2010. / Title from title screen. Includes bibliographical references.

The aim of his study was to investigate the role of Dctn2 in mouse preimplantation embryonic development, specifically its effect on the first cell fate decision, when the number of cells increases from eight to sixteen.

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

DNA methylation is one of the principal epigenetic modifications that plays an essential role in transcriptional regulation. After fertilization, mammalian embryos undergo dynamic changes in genome-wide DNA methylation patterns and the changes are essential for normal embryo development. Ten-eleven translocation (TET) methylcytosine dioxygenases are implicated in DNA demethylation by catalyzing the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). The three members of TET protein family, TET1, TET2, and TET3, are highly expressed in preimplantation embryos in a stage-specific manner. Previous studies demonstrated that TET proteins are involved in diverse biological processes such as gene regulation, pluripotency maintenance, and cell differentiation by mediating 5mC oxidation. My dissertation research was conducted to elucidate the mechanistic roles of TET proteins in epigenetic reprogramming of mammalian embryos using porcine embryos as a model. The first set of studies focused on the relationship between TET proteins and pluripotency. To understand the role of TET proteins in establishing pluripotency in preimplantation embryos, CRISPR/Cas9 technology and TET-specific inhibitors were applied. TET1 depletion unexpectedly resulted in an increased expression of NANOG and ESRRB genes in blastocysts, although the DNA methylation levels of NANOG promoter were not changed. Interestingly, transcript abundance of TET3 was increased in blastocysts carrying inactivated TET1, which might have had an effect on the increase of NANOG and ESRRB. When the activity of TET enzymes was inhibited to eliminate the compensatory increase of TET3 under the absence of functional TET1, the expression levels of NANOG and ESRRB were decreased and methylation level of NANOG promoter was increased. In addition, ICM specification was impaired by the inhibition of TET enzymes. These results suggest that the TET family is a critical component of the pluripotency network of porcine embryos by regulating expression of genes involved in pluripotency and early lineage specification. In the next set of studies, the presence of TET3 isoforms in porcine oocytes and cumulus cells was investigated to dissect the gene structure of TET3 that could assist in understanding mechanistic actions of TET3 in the DNA demethylation process. Among the three TET3 isoforms identified in cumulus cells, only the pTET3L isoform, which contains CXXC domain that carry DNA binding property, was verified in mature porcine oocytes. Expression level of the pTET3L isoform was much higher in mature oocytes compared to that in somatic cells and tissues. In addition, the transcript level of this isoform was significantly increased during oocyte maturation. These results suggest that pTET3L isoform is predominantly present in mature porcine oocytes and that CXXC domain may play an important role in DNA demethylation in zygotes. In a follow-up study, the role of the TET3 CXXC domain in controlling post-fertilization demethylation in porcine embryos was investigated by injecting TET3 GFP-CXXC into mature porcine oocytes. The injected CXXC was exclusively localized in the pronuclei, indicating that the CXXC domain may localize TET3 to the nucleus. The CXXC overexpression reduced the 5mC level in zygotes and enhanced the DNA demethylation of the NANOG promoter in 2-cell stage embryos. Furthermore, the transcript abundance of NANOG and ESRRB was increased in blastocysts derived from GFP-CXXC overexpressing zygotes. These results provide an evidence that the CXXC domain of TET3 is critical for post-fertilization demethylation of porcine embryos and proper expression of pluripotency related genes in blastocysts. In the last set of studies, the impact of MBD proteins on porcine embryo development was examined under the hypothesis that competitive binding of MBD and TET proteins to 5mC contributes to the proper maintenance of DNA methylation levels in embryos. Cloning of porcine MBD1, MBD3, and MBD4 from mature oocytes indicates that the genes are highly conserved among different species, implying the involvement of porcine MBD proteins in the maintenance of DNA methylation. MBD1 overexpression in oocytes impaired preimplantation development of porcine embryos, suggesting that the MBD1 overexpression may have negatively affected porcine embryo development because proper DNA methylation levels were not preserved under the high level of MBD1. Collectively, the studies in my dissertation demonstrate that TET family proteins are important epigenetic players involved in the regulation of pluripotency and reprogramming of DNA methylation, and are thus crucial for normal embryo development. The findings in the dissertation will improve our understanding of epigenetic events occurring in mammalian embryos, and have the potential to overcome epigenetic defects that are observed in pluripotent stem cells and in-vitro derived embryos. / Doctor of Philosophy / Epigenetic modifications are heritable changes affecting the level of gene expression without changing the sequence of the genome. DNA methylation, one of the biggest epigenetic marks in mammalian genome, is often correlated to gene repression. In mammals, DNA methylation patterns are dramatically changed during preimplantation development to acquire embryonic developmental potential. Understanding of the epigenetic changes occurring in preimplantation embryos is necessary for producing healthy domestic animals in agriculture and for developing strategies for the treatment of epigenetic defects in human. Ten-eleven translocation (TET) family enzymes, TET1, TET2, and TET3, are known to function as a DNA methylation modifier by converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). My dissertation research was performed to elucidate the role of TET family during preimplantation development using porcine embryos as a model. Pluripotency refers to the ability of cells to differentiate into all cell types of a mature organism. Pluripotent cells emerge in embryos as embryonic cells acquire lineage-specific characteristics. The first set of studies focused on the role of TET enzymes in regulating the pluripotency of porcine embryos. The impacts of inhibited activities of TET enzymes on the expression of pluripotency related genes were examined. We found that the inhibition of all TET enzymes leads to a decreased expression of pluripotency related genes, an altered DNA methylation level on a gene segment controlling pluripotency, and the impaired formation of pluripotent cell lineage in porcine embryos. This study demonstrates that the TET family is critical for the acquisition of pluripotency in porcine embryos. In the following sets of studies, the function of TET3 protein in the demethylation process occurring in preimplantation embryos was investigated. Fertilized mammalian embryos undergo genome-wide demethylation process to reset germ cell specific epigenetic marks into the embryonic epigenome. Previous studies indicate that TET3 is responsible for the demethylation process in mammalian embryos, although detailed mechanistic action of TET3 is still elusive. Here, we identified a predominant expression of a specific TET3 gene in porcine oocytes. The TET3 gene contained a CXXC domain, a potential DNA binding module, suggesting that TET3 may mediate DNA demethylation through its DNA binding property. To examine the function of the CXXC domain in TET3-mediated DNA demethylation, isolated CXXC domain was injected into porcine oocytes. The injection of CXXC domain facilitated DNA demethylation in embryos, demonstrating that the DNA binding property of TET3 is important for its functionality. In the last study, we investigated the importance of genes known to interact with TET enzymes in porcine embryos. Methyl-CpG-binding domain proteins (MBDs) have the ability to bind methylated region on the genome and play a critical role in mediating DNA methylation and gene repression. Our hypothesis was that a competitive binding of MBD and TET proteins to methylated regions was critical for proper DNA methylation levels in embryos. We identified that porcine MBD sequences were very similar to other species in terms of gene structure, indicating that the genes could also possess gene repressing activity by competing with TET enzymes during porcine embryo development. Injection of MBD1 mRNA to oocytes impaired normal embryo development, suggesting that the injected MBD1 may have negatively affected early embryo development in pigs by disrupting the proper maintenance of DNA methylation levels. My dissertation researches demonstrate that maintaining proper DNA methylation levels through the TET family is critical for normal embryo development in pigs. This research assists in improving our understating of epigenetic dynamics occurring in mammalian embryos and offers a potential solution to the epigenetic defects frequently observed in mammalian embryos produced through artificial reproductive technologies and pluripotent stem cells reprogrammed from somatic cells.